The Ishihara Color Blind Test is the most well-known and widely used diagnostic tool for identifying color vision deficiencies (CVD). It is most notable for detecting red-green color blindness. Named after its inventor, Dr. Shinobu Ishihara, the test was first introduced in the early 20th century and still remains an important tool in the field of ophthalmology.
Creation and Design
Dr. Ishihara, a professor at the University of Tokyo, created the Ishihara plates in 1917. The design of the test revolves around pseudoisochromatic plates, a collection of colored dots with varying sizes and hues.
Each plate features a hidden number or a line within a pattern of colored dots. For individuals with normal color vision, these patterns or numbers are easily distinguishable. However, for those with color vision deficiencies, these patterns can be difficult or even impossible to identify.
There are several different types of plates, including:
- transformation plates: people with red-green color blindness will see different numbers or no numbers at all.
- vanishing plates: people with normal color vision can see these numbers, while those with a color vision deficiency may not see any number.
- transformation plates specifically designed for red-green color blindness: people with normal color vision will see these numbers, while those with red-green color blindness will see different numbers or no numbers.
- diagnostic plates: designed to determine the type and severity of color blindness. They typically contain squiggly lines that individuals with specific color deficiencies will trace differently than those with normal color vision.
- control plates: contain one or several "X" shapes. All individuals, regardless of their color vision, should be able to identify the shapes. If not, this could indicate that the viewer did not understand the instructions or that the test was not administered properly.
Using the Ishihara Test
The Ishihara test is straightforward and quick, making it a convenient method for initial color blindness screening. The test-taker views one plate at a time and is asked to identify the number or trace the line within the dot pattern. The results are then compared with the known responses for color-deficient and normal vision.
In the Ishihara test, each plate serves a specific purpose to test an individual's color perception. The following descriptions are typical interpretations for each plate, providing insights into how to understand the results. The plates should be interpreted under appropriate (preferably natural, lighting conditions and with the guidance of a professional. It's worth noting that the test may not be as accurate when conducted online due to differences in screen calibrations and lighting conditions. The images and interpretations are based on 8 plates from a 38 plate test. Tests come in a multitude of sets with different configurations.
The following slide examples may appear different and have varying accuracy when seen on a digital screen. This is not an official test.
ISHIHARA TEST PLATE 1
Known as a demonstration plate, this plate is visible to all individuals, regardless of whether they have a color vision deficiency. This specific plate contains the number "12." If this number is not visible, it might indicate a problem with the test administration, such as improper lighting or incorrect viewing distance, or extreme farsightedness or vision loss in the patient.
ISHIHARA TEST PLATE 3
People with normal vision will see the number '6'. People with red-green deficient eyes will see the number '5'.
ISHIHARA TEST PLATE 7
People with normal vision will see the number '3'. People with red-green deficient eyes will see the number '5'.
ISHIHARA TEST PLATE 9
People with normal vision will see the number '74'. People with red-green deficient eyes will see the number '21'.
ISHIHARA TEST PLATE 10
People with normal vision will see the number '2'. People with red-green deficient eyes will see different numbers or no numbers.
ISHIHARA TEST PLATE 12
People with normal vision will see the number '97'. People with red-green deficient eyes will see different numbers or no numbers.
ISHIHARA TEST PLATE 13
People with normal vision will see the number '45'. People with red-green deficient eyes will see different numbers or no numbers.
ISHIHARA TEST PLATE 21
Not all people can see this number, but it might not be why you think. This slide is commonly known as a Reverse Color Blind Test. People with normal vision will see nothing. People with red-green deficient eyes will see the number '73'.
ISHIHARA TEST PLATE 23
People with normal vision will see the number '42'. Protonopia or protanomaly will see the number '2'. People with deuteranopia or deuteranomaly will see '4'.
Note: These images are only examples. This test should be administered by a healthcare professional who can provide a comprehensive eye exam.
Despite its popularity, the Ishihara test has limitations. It primarily identifies red-green color blindness, with less emphasis on other types of color deficiencies. Additionally, the test is not always effective in detecting less severe forms of color blindness.
Beyond their medical use, the principles of the Ishihara plates have found applications in fields like design and art, where they inspire creativity while raising awareness about color vision deficiencies.
They also play a role in safety, for example, testing airline pilot applicants, where color recognition and sharp vision acuity are a necessity.
The Ishihara test remains a major contribution to the field of ophthalmology, providing a simple and efficient method for detecting color vision deficiencies. It's widespread use for over a century testifies to its enduring utility, even as newer tests and technologies continue to enhance our understanding of color blindness.
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Last update: 2023-07-18